If Jesus took the punishment for all the sins of the world on the cross, why does God also punish people in hell? Isn’t God punishing the same sins twice? It reminds me of the master in Jesus’ parable who forgave his servant a large debt, but then made him pay it anyway.
I discussed the parable in my last post. To address the other part of your question, I wouldn’t say that people in hell are being punished a second time for sins that Jesus already took the punishment for on the cross. Jesus’ work on the cross is sufficient to atone for all of the sins of the world. But in order to receive the benefits of that atonement, people need to respond in faith and trust to what Jesus did.
It’s as if someone announced a huge relief fund for the victims of a natural disaster, a fund that would be sufficient to cover all of their losses. People would still need to apply to the fund to get benefits. If they didn’t apply, perhaps because they didn’t want to be beholding to anyone, or because they wrongly suspected the motives of the benefactors, they shouldn’t think that they were still suffering their losses because the fund wasn’t sufficient to cover them, or because the losses had to be paid for twice–once by the fund and then again by themselves. The explanation is that they didn’t apply.
In the same way, if people experience separation from God in hell, this is not because Jesus’ death wasn’t sufficient to pay for their sins, and not because God is making them pay for these sins a second time, but rather because they haven’t chosen to trust in Jesus’ work for their salvation.
I would add that the essential character of hell is separation from God. In effect, those who choose not to enter into relationship with God through Jesus’ work on the cross are choosing to live out of relationship with God. A holy God cannot have sin in His presence, and that’s why there’s a place where people who do not embrace God’s provision for the forgiveness of their sins live apart from God. Hell is also described as a place of suffering, but I don’t think its essential purpose is punishment. Rather, it’s separation. People who choose not to be restored to relationship with God are given what they have chosen–an existence apart from God.
I hope these thoughts are helpful in addressing your excellent and thoughtful question.